This invention is generally directed to processes for the preparation of quaternary ammonium compounds, and more specifically to economically feasible, large scale processes for the preparation of quaternary ammonium bisulfates. More specifically, the present invention is directed to the preparation of quaternary ammonium bisulfates, especially hydrogen sulfates, such as distearyl dialkyl ammonium bisulfates, by the reaction of the appropriate ammonium salt with sulfuric acid in a specific solvent mixture. The resulting products can be selected as additives, especially charge control additives for toner compositions, and in embodiments may be useful as antifungal components and surface active agents such as phase transfer catalysts. In developer and toner compositions, the aforementioned charge control additives impart or assist in imparting a positive charge to the toner resin particles and enable toners in some instances with rapid admix characteristics. These toner compositions usually contain pigment particles comprised of, for example, carbon black, magnetites, or mixtures thereof, cyan, magenta, yellow, blue, green, red, or brown pigments, or mixtures thereof, thereby providing for the development of black and/or colored images in electrophotographic, especially xerographic, imaging and printing processes, including color processes.
Developer compositions with charge enhancing additives, and processes for the preparation thereof in some instances, which additives impart a positive charge to the toner resin, are known. Thus, for example, the use of quaternary ammonium salts as charge control agents for electrostatic toner compositions is described in several U.S. Pat. Nos. such as: 3,893,935; 4,221,856; 4,312,933, a division of U.S. Pat. No. 4,291,111; 4,291,112; 4,298,672; 4,560,635; 4,675,118 and 4,812,381.
Toner and developer compositions with the quaternary ammonium salt compounds of the present invention are specifically illustrated in U.S. Pat. No. 4,937,157, the disclosure of which is totally incorporated herein by reference. Further, there are illustrated in U.S. Pat. No. 4,904,762, the disclosure of which is being totally incorporated herein by reference, toner and developer compositions comprised of a mixture of charge enhancing additives wherein one of the additives is an alkylammonium bisulfate as described herein.
Quaternary ammonium bisulfates (hydrogen sulfates) and methods of preparing thereof are described in the literature. A number of bisulfates with the generic formula (R.sup.1).sub.3 R.sup.2 N.sup.+ HSO.sub.4 --, and more specifically tetraalkylammonium bisulfates (C.sub.3 -C.sub.6) and aryltrialkylammonium bisulfates, and methods for the preparation thereof are described by A. E. Brandstrom et al. in U.S. Pat. No. 3,816,533. In a first synthetic scheme, a quaternary ammonium iodide was obtained from an alkyl iodide and the corresponding alkylamine in acetonitrile, and then reacted with dimethyl sulfate to produce a tetraalkyl or aryltrialkylammonium methylsulfate. After removal of the solvent by distillation, water and a catalytic amount of sulfuric acid was added and the mixture was allowed to boil for 24 hours while distilling off methanol. Subsequent to evaporation to dryness, the crude bisulfate was purified by recrystallization. A second route involves the reaction of a tetraalkylammonium hydroxide with a molar equivalent of sulfuric acid, the evaporation of the resulting solution to dryness and the recrystallization of the crude bisulfate from methyl ethyl ketone. In another method described in U.S. Pat. No. 3,816,533, a tetraalkylammonium bromide is reacted with pentachloropheaol in a two phase organic-aqueous solvent system in the presence of sodium hydroxide. The resulting tetraalkylammonium phenolate is then reacted with aqueous sulfuric acid, the aqueous solution evaporated and the bisulfate found in the residue reprecipitated from a solvent such as methyl isobutyl ketone. Yet another method described in the aforementioned U.S. patent involves the preparation of certain quaternary ammonium bisulfates by reacting a quaternary ammonium halide with sulfuric acid and hydrogen peroxide. The reaction mixture can be filtered, the filtrate evaporated in vacuum and the residue redissolved in an organic solvent to recover the bisulfate by recrystallization.
A variant of the aforementioned first method, that is the dimethyl sulfate method, Is detailed in "Preparative Ion Pair Extraction", Apotekarsocieteten/Hassle, Lakemedel, Sweden, 1977, pages 139 to 148 by A. Brandstrom and reproduced by C. M. Starks and C. Liotta in "Phase Transfer Catalysis, Principles and Techniques", Academic Press, New York, 1978, pages 76 to 77. This procedure involves the Use of several organic solvents in a multi step process, in particular chlorobenzene, dioxane and petrol ether.
An ion pair extraction method is also described in the aforementioned textbooks. For example, a tetraalkyl ammonium iodide, trioctylamine and sulfuric acid are reacted in a two phase toluene-water solvent system. The aqueous phase containing the bisulfate is extracted with an organic solvent such as methylene chloride to remove excess tetraalkyl ammonium halide and the excess of sulfuric acid as an ion pair with trioctylamine. Water was removed at reduced pressure and the residue was recrystallized from methyl isobutyl ketone to obtain the pure quaternary ammonium bisulfate.
Dehmlow et al. in Syntheses, 1985, pages 508 to 509, indicates that most of these methods work well for tetrabutyl ammonium derivatives, but they cannot be extended to more hydrophobic (lipophilic) ammonium bisulfates. Alternative methods for obtaining more hydrophobic tetraalkyl ammonium bisulfates were pursued by Dehmlov et al. One of these methods involves the synthesis of tetraalkyl ammonium thiocyanates and their reaction with relatively concentrated sulfuric acid. Byproducts of the reaction include H.sub.2 S, CO.sub.2, CS.sub.2 and HSCN, and a rather involved work-up procedure is required to isolate the bisulfate. Another method, described by De Giorgi et al., Synthetic Communications, 17(5), 1987, pages 52 to 533, requires the reaction of sulfuric acid with quaternary ammonium azides. The quaternary ammonium azides, in turn, have to be prepared from quaternary ammonium methane sulfonates by reaction with sodium azides.
The prior art methods are rather complicated, not easily conducive to scale-up, nor do these methods usually provide for an economically feasible commercial process, problems avoided or minimized with the processes of the present invention.
Another procedure for Producing quaternary ammonium hydrogen sulfate, specifically tetrabutylammonium hydrogen sulfate, is described in U.K. Patent Application 2,073,748. The method proposed involves the reaction of quaternary ammonium halide with sulfuric acid in the presence of an alcohol. After completing the reaction by heating to reflux, the byproduct, butyl bromide, was removed by distillation together with some of the alcohol used in the reaction. The proposed recovery of the bisulfate from the residue involves the extraction with methylene chloride, evaporation to dryness of the organic phase and recrystallization from methyl isobutyl ketone.
Disclosed in copending patent application U.S. Ser. No. 396,497 now abandoned, the disclosure of which is totally incorporated herein by reference, the disclosure of which is totally incorporated herein by reference, is a process for the preparation of distearyl dimethyl ammonium bisulfate by a process for the preparation of quaternary ammonium compounds of the formula R'.sub.2 R".sub.2 N.sup.+ X-- wherein R' and R" are independently selected from the group consisting of alkyl, aryl, and alkylaryl; and X- is an anion, which comprises the reaction by heating a water insoluble quaternary ammonium salt with an acid.